This relates generally to image sensors, and more specifically, to methods and circuitry for testing the integrity of the components in the image sensor.
Image sensors are commonly used in electronic devices such as cellular telephones, cameras, and computers to capture images. Conventional image sensors are fabricated on a semiconductor substrate using complementary metal-oxide-semiconductor (CMOS) technology or charge-coupled device (CCD) technology. The image sensors may include an array of image sensor pixels each of which includes a photodiode and other operational circuitry such as transistors formed in the substrate.
Over the lifetime of an electronic device, image sensors in the electronic device may be prone to failure. Conventional image sensors are sometimes provided with methods and circuitry for testing the functionality of the image sensor. However, including circuitry for testing the functionality of the image sensor may lead to a complex manufacturing process for the image sensor. Additionally, in conventional image sensors, a single semiconductor substrate is used for the image sensor. This may reduce the amount of space available for the pixel photodiodes.
It would therefore be desirable to be able to provide improved image sensors that include circuitry for testing the functionality of the image sensor.